Abstract: The invention disclosed is related to a composition for the control of molluscs wherein an effective amount of infective dauer larvae of Phasmarhabditis nematodes which have been cultured with a nematode growth promoting and pathogenicity-inducing bacterium, as well as a carrier or encapsulation agent are provided as the ingredients for the composition. Further, the composition can be used in the form of a water-dispersable powder comprising as the carrier a calcium montmorillonite clay. The nematode concentration in the water-dispersable powder is 0.1.times.10.sup.6 to 2.0.times.10.sup.6 per gram of total composition (wet weight), and preferably from 0.3.times.10.sup.6 to 0.8.times.10.sup.6 per gram of the total composition (wet weight). Further, the nematodes are selected from amongst the species P. neopapillosa or P. hermaphrodita. The growth promoting bacterium is a Moraxella osloensis strain or Pseudomonas fluorescens strain.